This invention relates to control systems for vapor-discharge lamps and, more particularly, to a control system which automatically dims the lamps after a predetermined time when a lower degree of illumination can be tolerated, and then, automatically brightens the lamps for the remainder of the night to accommodate early morning traffic.
In recent years much effort has been directed toward developing lighting systems that are energy-conserving. Present day outdoor lighting systems, such as those used for street lighting and parking areas waste energy because these systems were not designed to operate at more than one power consumption level. There have been attempts to conserve energy with these present systems such as, turning a portion of the lights in a system completely off. This approach though conserving energy may be a safety hazard because of the poor lighting distribution that may result. The aforesaid copending application Ser. No. 861,591 is an improvement over such approach because it provides for automatic dimming of an entire lighting system with uniform light distribution. The aforesaid copending application Ser. No. 861,587 is a further improvement because, as already stated, it automatically compensates for the seasonal variations in the length of night. The present invention automatically provides for a higher degree of illumination for early morning traffic during that period of the year when the "rush hour" begins while it is still dark.